Electrical conductors are utilized in various applications from transmitting data signals to providing a connection across which electrical current may flow. Contacts between two transmitters of electrical current or data signals allow the electrical current or data signals to be transmitted from one conductor to another.
Prior art connectors have included nickel-gold plated copper conductors. However, pitting corrosion has occurred in such constructions that have resulted in the deterioration of the contacts, which in turn has adversely affected electrical performance. While the nickel layer has been used as a buffer layer between the outer gold plating layer and the copper substrate, pitting corrosion occurs through the nickel-gold layer due to pin holes extending through the gold plating layer and nickel plating layer.
One solution to the pitting problem has been to apply a seal plating layer between the nickel layer and the copper layer. The seal plating layer preferably has been tin (Sn) applied over the copper substrate and in contact with the nickel (Ni) plating layer. After application, the Sn forms an intermetallic with Cu as well as with Ni at its interface with each of these materials. The intermetallic layers are formed either as a result of solid state interdiffusion, which may occur either at room temperature or as a result of an elevated temperature heat treatment, or as a result of Sn reflow. Intermetallic materials are very corrosion resistant, but are also significantly harder and less ductile than the copper substrate over which the Sn is applied, or the Ni or nickel alloys applied over the Sn. The thickness of the intermetallic materials formed by heat treatment or Sn reflow creates an intermetallic layer that is also brittle. Thus, while this solution has solved the problem of pitting, delamination occurs at the thick and brittle intermetallic layer between Ni and Sn, and from the readily formed thin Sn oxide layer from the exposure of Sn to the atmosphere between the Sn and Ni plating operations.
What is needed is a solution to both the delamination problem and to the pitting problem created by the use of Au/Ni applied over copper substrates or Au/Ni/Sn applied over copper substrates.